From my side...with the B4 photos at this Worldchampionship, ...I only see a "classic weight balance" :
For Neil car:
- 18gr on the rear bulkhead ( additional weight included on the B4.1 kit )
- 5gr on each rear corner
-14gr on Servo & 7 on front
...for the Ryans
Maifield : same as Neil's "rear end" ( total 28gr ), 7g on each front corner ( close the servo ).
Cavaleri : same as Neil's "rear end" and no more additional weight.
For the batteries, each use reedy batteries ( #628 ) = 307g
But I wasn't under the Lipo to verify...and with the "BIG" jumps...a light car is better.
I'm not sure that one day we will get the B4.1's setups on internet.
PS: We can also talk about the springs that Cav' was using on rear and Neil fronts "curious yellow w/o paint" springs...it could be another thread
K springs ?